Known foam producing devices as for example in U.S. Pat. No. 3,709,437 employ a deformable reservoir containing foamable liquid and air, a discharge orifice, foam producing means including a foam homogenizing overlay or filter, and a ball check valve disposed in the foam producing means. The means also has air passages in a well portion which defines a mixing chamber. When the reservoir is compressed, the liquid and air are mixed in the chamber. The mixture is passed through the overlay to produce foam which is then discharged through the orifice. The check valve prevents downward flow of the liquid after the compression force in the reservoir is released, thus reducing the time to produce foaming upon subsequent compression. While the reservoir is returning to its uncompressed state after the compression force is released, air flows from outside the device in reversed direction through the same air passages into the reservoir for use in subsequent foam producing operations. These known devices provide separate passages for air and liquid to flow upward to the chamber when the reservoir is compressed.
Normally these devices are held in vertical position. However, if such a device is tilted appreciably from the vertical in use, as for example at an angle of 45.degree., depending upon the relative levels of air and liquid in the reservoir, the air may flow upward through the passage used to conduct liquid while the liquid may flow upward through the passage used to conduct fluid. The passages used for air differ in length and cross sectional area differ from those used for liquid whereby this interchange of passages creates blockages and other malfunctions.
Sometimes the device will not function at all thereafter. At the very least, the device must be returned to vertical position and the reservoir squeezed and released repeatedly until normal functions is restored.
This invention overcomes these disadvantages by preventing such interchange of passages for air flow and liquid flow.